Dynamic disk volumes cannot be added to pool

[Carsten]

I have WHS2011 on a HP x510 and mirrored the system drive (60GB) on two hard drives to guard against a system drive failure. The rest of the two harddrives have data partitions d: and e:, which are not mirrored, but simple volumes. Unfortunately I am not able to add these two volumes to the drive pool. Why? What special things is drivepool doing, that it cannot use these two volumnes? Is there a trick to add them and would there be negative consequences?

[Christopher (Drashna)]

We don't support adding Dynamic disks (or volumes) to the pool. To add them, they need to be "Basic" disks.

 

There are a few reasons for this, but namely we use "VDS" and it doesn't display the disks correctly that way. 

[Carsten]

We don't support adding Dynamic disks (or volumes) to the pool. To add them, they need to be "Basic" disks.

 

There are a few reasons for this, but namely we use "VDS" and it doesn't display the disks correctly that way. 

Tha'ts really a pity. I think most Homeservers have 3-6 disks, and two of them are lost for storage, if you want to protect 60GB of the system partition by mirrorring. In my case of an HP-x510 with 4 drives, I had lots of reinstallation problems due to failed systems disks in the past,  so I want the system partition secured by mirroring (only 60GB of 2000 GB of the two drives). But then I loose almost 2 x 2TB storage space, because I cannot use the simple volumes of 1940GB it in DrivePool.

 

Could you please rethink to support dynamic disks? It would not be necessary to support mirrored or extended volumes just simple volume which reside on a dynamic disk (the disk is dynamic because a small part, the system partition, is mirrored).

[Christopher (Drashna)]

The problem is that, there is no "halfies". Either it's a dynamic disk or it's not. Even if it's just a simple volume on the disk, BECAUSE it's a dynamic disk, it makes it significantly harder to deal with. 

 

If you want to see what I mean, run diskpart, "list disk", "select disk #" (where the number is one of the dynamic disks), "list partition".

All this will list is dynamic disk information.

 

 

I've flagged Alex (the developer) for a more detailed answer about why.

 

Additionally, there is a reason that a lot of people (myself included) recommend a small, dedicated drive for the system disk. 

One reason is for SSDs. They really do make a difference. Also, a dedicated drive for the system means that there is less impact on the pool, as you are not dividing IO between the system (which can be intensive and consistent, especially because of the page file). Additionally, you can use Windows Server Backup to backup and restore the system with a lot more ease, as as you're only worried about the data on one drive.

 

But yes, that means you effectively lose one "bay" in the MediaSmart Server (or DataVault).

[Carsten]

Actually I loose two bays. Because the x510 are headless servers (impossible or at least very difficult to attach a keyboard and screen) restore is really complicated and costs hours of work. I had this problem with several servers and decided to go for WHS2011 and disk mirroring of the system drive. Then I loose 2xTB of storage space in drive pool.

 

I looked at the diskpart information, but it looks quite normal (one NTFS partition):

 

DISKPART> list partition
  Partition ###  Typ               Größe    Offset
  -------------  ----------------  -------  -------
  Partition 1    Dynamische Daten   931 GB    31 KB
 

 

The other drive with three partitions look a little different: There seems to be a 992KB pseudo partition which is not in the disk manager. Apart from that it also looks not strange:

 

  Partition ###  Typ               Größe    Offset
  -------------  ----------------  -------  -------
  Partition 1    Dynamische Daten   992 KB    31 KB
  Partition 2    Dynamische Daten   100 MB  1024 KB
  Partition 3    Dynamische Daten    60 GB   101 MB
  Partition 4    Dynamische Daten  1802 GB    60 GB

 

So what is the problem?

[Christopher (Drashna)]

Ah, it looks like you converted the disk afterwards, and it retained the partitioning. 

However, I've attached an image of what it looks like if you create the disk as dynamic.

The ~300GB partition was mirrored, and the rest of the space was two separate volumes. Take a look at what diskpart shows in this case:

 

 

[Carsten]

Yes new dynamic disk use only one (MBR) or two (GPT) partitions to store all data and metadata. You only have "volumes" no partitions any more. If you type "detail disk" you see  the volumes on the selected disk. Here is a good article on the disk layout on dynamic disks: http://www.howtogeek.com/school/using-windows-admin-tools-like-a-pro/lesson4

 

My questions is: What does DrivePool has to do with partitions? Shouldn't it only look at volumes?

[Christopher (Drashna)]

The answer is dead simple:

 

Which volume do we store the duplicate on?

 

We specifically look for the information so we know what physical disk the files are on, so we can actively avoid placing the duplicate files on the same physical disk, if it has multiple partitions.

 

Additionally, This is important in the case of damage to the disk, and using the StableBit Scanner balancer to evacuate the disk.

[Carsten]

Yes as you said, you have to know on which disks are files stored. The hierarchy is as follows:

 

Files are stored on filesytems

-> Filesystems are stored on volumes

-->  Volumes are are stored on either partitions or dynamic disk space

--->  Partitions and dynamic diskspaces are stored on disks

 

You are only interested in volumes (containing files) and disks, but not on the middle part of partitions and dynamic disk space, so you can query directly for volumes and disk.

 

In diskpart (but also possible with Windows API of course):

Query for all volumes: list volumes

Query for all disks: list disk

Query which volumes a disk contains, e.g. disk 3:

   select disk 3

   detail disk

[Carsten]

bump

[Christopher (Drashna)]

Just to let you know, I've talked with Alex directly about this, and once he has more time, he is going to look at seeing about including Dynamic Disk support.  I can't really give you an ETA on this, but it is on our to-do list.

[Carsten]

Are there any news to solve the problem? The fix should not be too difficult.

[Christopher (Drashna)]

Are there any news to solve the problem? The fix should not be too difficult.

No there isn't yet. We've been busy working on StableBit CloudDrive, so we haven't been able to focus on getting out any major code changes to DrivePool.

 

As for implementing... it's a lot more complicated than you'd think.

While allowing dynamic disks would be very simple.... ALL of the code for Duplication would have to be tweaked, and the balancing engine would have to be overhaul. 

The big thing is that we prevent duplicate files from being placed on the same physical disk. This ALONE makes a huge problem with the duplication and balancing code.